Verification of step-backwater computations on ephemeral streams in northeastern Wyoming

Step-backwater computations were verified by subsequent discharge measurements at three ephemeral streamflow stations in northeastern Wyoming. The standard step-backwater method for gradually varied, subcritical flow was used in computing the water-surface profiles and stage-discharge ratings. Step-backwater computations were made at selected intervals from I through 1,000 cubic feet per second on Lodgepole Creek, through 150 cubic feet per second on Raven Creek, and through 600 cubic feet per second on Sand Creek. Stage-discharge rating curves and discharge measurements are illustrated for the three sites, with lines of 15-percent departure from the rating curves drawn to measure accuracy of the results. All discharge measurements showed departures of less than 15 percent at the high end of the rating curves.